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(Name, Address and Telephone Number of Person Authorized to Receive Notices and Communications)

August 29, 2017

(Date of Event Which Requires Filing of Statement)

If the filing person has
previously filed a statement on Schedule 13G to report the acquisition that is the subject of this Schedule 13D, and is filing this schedule because of Rule 13d-1(e), Rule 13d-1(f) or Rule 13d-1(g), check the following box. ☒

Note. Schedules filed in paper format shall include a signed original and five copies of the schedule, including all exhibits. See Rule 13d-7(b)
for other parties to whom copies are to be sent.

*

The remainder of this cover page shall be filled out for a reporting persons initial filing on this form with respect to the subject class of securities, and for any subsequent amendment containing information
which would alter disclosures provided in a prior cover page.

The information required on the remainder of this cover page shall not be
deemed to be filed for the purpose of Section 18 of the Securities Exchange Act of 1934 (Act) or otherwise subject to the liabilities of that section of the Act but shall be subject to all other provisions of the Act
(however, see the Notes)

Based on 46,650,699 shares of Common Stock of Acorda Therapeutics, Inc. (the Issuer) outstanding as of July 31, 2017, as reported in the Issuers Form 10-Q filed with the Securities and Exchange
Commission (SEC) on August 8, 2017.

All capitalized terms contained herein but not
otherwise defined shall have the meanings ascribed to such terms in the Schedule 13D. Information given in response to each item shall be deemed incorporated by reference in all other items, as applicable.

ITEM 3.

SOURCE AND AMOUNT OF FUNDS OR OTHER CONSIDERATION

Item 3 of the Schedule 13D is hereby amended and
restated as follows:

The aggregate purchase price of the shares of Common Stock directly held by the Investment Vehicles reported herein was
$192,847,617.94. The shares of Common Stock directly held by the Investment Vehicles were purchased with the working capital of the Investment Vehicles (which may, at any given time, include margin loans made by brokerage firms in the ordinary
course of business). All shares of Common Stock reported herein were purchased in open market transactions through a broker.

ITEM 4.

PURPOSE OF TRANSACTION

Item 4 of Schedule 13D is supplemented and superseded, as the case may be,
as follows:

This Amendment No. 1 is being filed to report acquisitions of beneficial ownership of shares of Common Stock in an amount equal to one
percent or more of the Issuers outstanding Common Stock since the Reporting Persons filed the Schedule 13D. The disclosure in Item 5(c) below regarding transactions in the Issuers Common Stock effected during the previous 60 days is
incorporated by reference herein. Consistent with their investment purpose, the Reporting Persons may make, or cause, further acquisitions of Common Stock from time to time and may dispose, or cause to be disposed, additional shares of Common Stock,
in each case depending on market conditions and other factors.

The Reporting Persons intend to review their investment in the Issuer on a continuing
basis and may from time to time and at any time in the future depending on various factors, including, without limitation, the outcome of any discussions with directors and officers of the Issuer, the Issuers financial position and strategic
direction, actions taken by the Board, price levels of the Issuers securities, other investment opportunities available to the Reporting Persons, conditions in the securities market and general economic and industry conditions, take such
actions with respect to the investment in the Issuer as they deem appropriate. These actions may include: (i) acquiring additional shares of Common Stock and/or other equity, debt, notes, other securities, or derivative or other instruments
that are based upon or relate to the value of securities of the Issuer (collectively, Securities) in the open market or otherwise; (ii) disposing of any or all of their Securities in the open market or otherwise; (iii) engaging
in any hedging or similar transactions with respect to the Securities; or (iv) proposing or considering one or more of the actions described in subsections (a) through (j) of Item 4 of Schedule 13D.

Except as set forth herein or previously disclosed in the Schedule 13D, the Reporting Persons do not have present plans or proposals at this time that relate
to or would result in any of the transactions described in subparagraphs (a) through (j) of Item 4 of Schedule 13D.

ITEM 5.

INTEREST IN SECURITIES OF THE ISSUER

Item 5 of the Schedule 13D is hereby amended and restated as
follows:

(a) and (b) Items 7 through 11 and 13 of each of the cover pages of this Schedule 13D are incorporated herein by reference. Such information
is based on 46,650,699 shares of Common Stock outstanding as of July 31, 2017, as reported in the Issuers Form 10-Q filed with the SEC on August 8, 2017.

Page 7 of 9 – SEC Filing

The Investment Vehicles have delegated to Scopia Capital sole voting and investment power over the securities
held by the Investment Vehicles pursuant to their respective Investment Management Agreements with Scopia Capital. As a result, each of Scopia Capital, Scopia Management, as the general partner of Scopia Capital, and Messrs. Sirovich and Mindich, as
Managing Directors of Scopia Management, may be deemed to exercise voting and investment power over the shares of Common Stock directly held by the Investment Vehicles. The Investment Vehicles specifically disclaim beneficial ownership of the
securities of the Issuer directly held by them by virtue of their inability to vote or dispose of such securities as a result of their respective Investment Management Agreements with Scopia Capital.

(c) Except as set forth on Schedule A attached hereto or previously disclosed in the Schedule 13D, there have been no transactions in shares of Common
Stock during the 60 days prior to the date hereof by any of the Reporting Persons. The information set forth on Schedule A is incorporated herein by reference.

(d) The disclosure regarding the relationship between the Reporting Persons in Item 2(c) of this Schedule 13D is incorporated by reference herein. All
securities reported in this Schedule 13D are directly held by the Investment Vehicles, all of which are investment management clients of Scopia Capital. None of the Investment Vehicles individually directly holds more than 5% of the Issuers
outstanding shares of Common Stock. The limited partners of (or investors in) each of the Investment Vehicles have the right to participate in the receipt of dividends from, or proceeds from the sale of, the shares of Common Stock held for the
accounts of their respective Investment Vehicles in accordance with their respective limited partnership interests (or investment percentages) in their respective Investment Vehicles.

Page 9 of 9 – SEC Filing

SCHEDULE A

TRANSACTIONS

Except as previously
disclosed in the Schedule 13D, the following table sets forth all transactions by the Reporting Persons (on behalf of the Investment Vehicles) with respect to shares of Common Stock effected in the last 60 days, inclusive of any transactions
effected through 4:00 p.m., New York City time, on August 30, 2017. Except as otherwise noted below, all such transactions were purchases of Common Stock effected in the open market, and the table excludes commissions paid in per share prices.